When sending uplink data or initiating a circuit-switched call, a terminal needs to send a channel request message to a network through a random access channel (RACH, Random Access Channel), so that the network assigns a packet resource to the terminal. The method specifically is: A terminal sends a channel request message, where the channel request message may be a channel request (Channel Request), a GPRS packet channel request (GPRS Packet Channel Request), or an enhanced data rates for GSM evolution packet channel request (EGPRS Packet Channel Request); and a network receives the channel request message sent by the terminal, and feeds back an immediate assignment message (IA, Immediate Assignment) on an access grant channel (AGCH, Access Granted Channel), so as to assign a packet resource for the terminal that sends the channel request message, where assigning the packet resource for the terminal is allocating a physical channel for a packet service of the terminal, the IA message needs to carry resource parameters of the allocated physical channel, and these parameters for assigning a packet resource are called as packet resource parameters. The IA message is a message that has at-most-176-bit valid information, which includes 16 bits for recording a frame number (the frame number is a), 8 to 11 bits of the total bits (Channel Request) for recording a channel request message, and the rest bytes for recording the packet resource parameters. Therefore, the length of the IA message only can be used to assign a resource parameter for one terminal. The terminal monitors, on the AGCH channel, the IA message fed back by the network and parses the IA message, and determines whether a resource allocated by the IA message is for the terminal by comparing a field (the frame number a and the channel request) carried in the IA message with a channel request message sent by the terminal and a frame number of a frame that sends the Channel request message, so as to successfully obtain the resource allocated by the IA message; and if not, ignores the IA message.
Because a channel request sent by the terminal may be lost due to a radio interference noise or has a collision with a channel request initiated by another terminal, the network cannot successively receive the channel request sent by the terminal. In this way, if the terminal does not receive a response of the network in an S period, the terminal may re-initiate a channel request. A rule for re-initiating a channel request by the terminal is described as follows: The terminal can send, on the RACH, the channel request for M+1 times at most, where the parameter M is broadcast by the network and is controlled by the network. After the terminal re-sends the channel request for the Mth time, regardless whether it is successful or not, this access process is ended and the access request is not re-sent. The number of TDMA frames in an interval between next time for sending the channel request and last time for sending the channel request is randomly selected from {S, S+1, S+T-1}, where T is a parameter “Tx integer” (Tx_integer) broadcast on a BCCH, and a value of S is determined by the configuration of a CCCH, and the value of S is shown in the following Table 1:
TABLE 1TxUncombined CCCHCombined CCCH/SDCCH3, 8, 14, 5055414, 9, 1676525, 10, 20109586, 11, 25163867, 12, 32217115
In a general case, if the IA message monitored by the terminal is a response to any one of last three channel requests of the terminal, it is considered that the IA is valid, then re-initiation of the channel request message is stopped, and a service is performed on an assigned channel.
With the development of communications technologies, “machine” to “machine” (M2M, Machine to Machine) communication connects various endpoint devices or subsystems at everywhere through multiple communications technologies and gathers them to a management system, so as to implement management and service for a device. At present, communication relevant to a “machine” is collectively referred to as machine type communication (MTC, Machine Type Communication).
Currently, a case that a large number of MTC terminals randomly initiate an access request exists.